[c-nsp] Help with multilink ppp, routing not working correctly..

[Howard Leadmon]

 I can't believe this one isn't working, I am sure I am looking over
something stupid.  I needed to mux up 3x T1's between a location.


Information is as follows: (relevant bits)

Location-A:   Cisco 1720
!         
interface Serial0
 description To Location-B
 ip address 38.103.8.238 255.255.255.252
!         
ip route 0.0.0.0 0.0.0.0 38.103.8.237
!




Location-B:  Cat5500 RSM   
!
interface Multilink1
 description T1 MultiLink PPP Bundle to Location-C
 ip address 192.168.98.29 255.255.255.252
 ppp multilink
 multilink-group 1
!
interface Serial1/2:1
 description To Location-A
 ip address 38.103.8.237 255.255.255.252
! 
interface Serial1/5:1
 description T1 3 of 3 (MultiLink)
 no ip address
 encapsulation ppp
 ppp multilink
 multilink-group 1
!         
interface Serial1/6:1
 description T1 2 of 3 (MultiLink)
 no ip address
 encapsulation ppp
 ppp multilink
 multilink-group 1
!         
interface Serial1/7:1
 description T1 1 of 3 (MultiLink)
 no ip address
 encapsulation ppp
 no fair-queue
 ppp multilink
 multilink-group 1
!         
ip route 0.0.0.0 0.0.0.0 to global internet gateway!



Location-C: Cisco 6509 Sup2 w/FlexWan
!
interface Multilink1
 description T1 Bundle to Corporate
 ip address 192.168.98.30 255.255.255.252
 ppp multilink
 multilink-group 1
!
interface Serial3/0/0:0
 description T1 1 of 3 no ip address
 encapsulation ppp
 no fair-queue
 ppp multilink
 multilink-group 1
!
interface Serial3/0/1:0
 description T1 2 of 3 
 no ip address
 encapsulation ppp
 ppp multilink
 multilink-group 1
!
interface Serial3/0/2:0
 description T1 3 of 3 
 no ip address
 encapsulation ppp
 ppp multilink
 multilink-group 1
!
ip route 0.0.0.0 0.0.0.0 192.168.98.29
!



The interfaces are up and running, the multilink bundle looks good, and if I
ping or trace from A to B, or B to A life is good.   If I try and go from B
to C or C to B, again life is good.   If I try and go from A to the internet
via B, or from C via B to the internet all is good.  So it looks like all is
working.  

Where I get bit, is if I try and go from A to C, or C to A.  I can not ping,
and if I trace it dies on router B.   So it looks like single hop is good,
and if I go to another location out off of B (other networks) all is good,
but if I try and cross any other internal interface on the router and cross
the MLPPP link it dies.

I was just going to use CEF to handle the link with per-packet load sharing
with a dynamic routing protocol, but apparently the FlexWan controller
doesn't support it, or it barked about an unknown command.  Anyway trying to
debunk this I stripped it back to the above, just static routes between
A-to-B-to-C, and still it will not route. This is part of a larger network,
and none of the other remote enpoints will cross that multilink line, and I
can't pin down why.

I am open to any suggestions, as I rarely use MLPPP, and am sure I am
missing something, but damn I would think two simple hops with static routes
should just go.   Thanks to any that can offer assistance on debunking this
one..


P.S. - Yes I know I have some routable, and some unroutable IP's, but this
is all behind a firewall, and gateways out, I just haven't gotten them to
pull the old public IP's out, granted that shouldn't matter for an internal
(in essence) isolated network.



---
Howard Leadmon